Radio frequency tuners can be found in a lot of devices, starting with TV sets, set top boxes and PC tuner cards. A tuner is a device that takes a ”chunk” of a frequency carrier of a bandwidth, amplifies it and then shifts it (usually by down-converting) into a fixed frequency that will be fed into a demodulator device. Tuners are difficult to build and a DIY tuner will never have the performance of one from a radio receiving device. The RF signal enters a baseband amplifier. Further, this signal is mixed with a local oscillator with variable frequency. The result exits the tuner as Intermediate Frequency (IF). Sometimes the tuner also contains a filter at the IF output. These functional blocks can be integrated into a superheterodyne receiver with ease (just add a detector). So, what can you do with a tuner? Keep reading.

Air TV channels broadcast on frequencies ranging from 170 MHz to 860 MHz. The VHF-Hi band covers 175 to 230 MHz, while UHF covers 470 to 860 MHz. The gap between is used for cable TV. Receiving all these frequencies is difficult when using a single antenna.

The Gray-Hoverman antenna has been designed by Doyt R. Hoverman and it was patented in the sixties. His design only covered a part of UHF band. However, with some improvements, the antenna can receive well both the UHF as well as VHF-Hi. This post will a simple to build variant of the antenna that can be used to receive 170 to 230 MHz channels (5 - 12) and a part of UHF between 470 - 720 MHz (21 - 52 channels) with a minimum gain of 5 - 6 dBi. There are however designs that offer a minimum gain of 8 dBi on VHF and 10 dBi on UHF (check the Links section). This antenna can be used for any kind of signal that can be received on the mentioned frequencies: analog TV, DVB-T, DVB-T2, ISDB-T, ATSC. The design is distributed according to the GNU GPL version 3 license.